A number of embodiments of variable focus liquid lenses are described in commonly assigned European patent No1166157. FIG. 1 of the present application corresponds to FIG. 12 of that patent. As shown in FIG. 1, an optical lens comprises two insulating transparent plates 100 and 102. Plate 102 comprises a conical or cylindrical recess, with a side face 104 inclined with respect to the optical axis Δ of the device, and which receives a drop of an insulating liquid 106. The remainder of the chamber extending up to transparent plate 100 is filled with a second liquid 108, which is conductive. The liquids are immiscible, and have different refraction indexes but roughly the same density. A transparent electrode 110 is formed over the outer surface of transparent plate 102. Another electrode 112 is provided in contact with a liquid 108.
Due to the electrowetting effect, it is possible, by applying a voltage between electrodes 110 and 112, to change the curvature of the interface between the first liquid 106 and the second liquid 108, for example, from an initial concave shape as shown by line A, to a convex shape as shown by line B. Thus rays of light passing through the cell perpendicular to the plates 100 and 102 in the region of the drop 106 will be focused more or less depending on the voltage applied.
When manufacturing a variable lens as shown in FIG. 1, it is necessary for the electrode 110 to be electrically insulated from the conducting liquid 108, and also for the liquids to be tightly sealed within a container.
International patent application WO 2005/073779 shows a variable focus lens package using sealing rings to seal the fluid chamber and thus preventing fluids to leak out of said chamber.
But the applicant has shown that the pressure applied by the liquids on their container can be very high during the manufacturing process or during subsequent use due to the manufacturing process or if the device is subjected to high temperature. If an inadequate seal is provided, liquid can escape the lens thus resulting in a degradation of the optical performance of the lens. Therefore, a specific seal is required, that can undergo the pressure applied by the liquids. Furthermore, the liquids 108 and 106 can be corrosive to certain materials, making many materials unsuitable for sealing the lens, thus limiting the choice of materials that can be used.
There is thus a need for a variable lens housing and a method of manufacturing the same, which provide a very hermetic seal so as to prevent leakage during the life of the lens, including when the pressure applied by the liquids is high, still keeping the lens easy to manufacture.